Ok, here's some results ....
Tailcap amp measurements (using 14 gauge high qual custom leads):
TrustFire 26650: 2.45A
KK ICR 4200: 2.51A
SONY 50A 26650: 2.52A
Efest 25A 18650: 2.51A
Samsung 20R: 2.50A
Powerizer: 2.50A
Amp measurements are pretty tightly grouped, so suspect it's fairly well regulated to 2.45-2.50 amps. Most of these cells are pretty hot cells, so there is definite amp limits in this driver.
Using the KK ICR 4200 for output measurements, Yezl Y3, XM-L2 T6:
lumens: 901 @start, 874 @30 secs, throw (from 5m): 62.6 kcd
Reference stock HD2010 TangsFire w/TF 26650, XML T6, measured 3.6A tail:
lumens: 908 @start, 898 @30 secs, throw (from 5m): 57 kcd
Certainly the HD2010 at the higher amps performs pretty good, but the Yezel still beats it in throw. The throw to lumens ratio goes to the Yezl, but of course it has the XM-L2 vs. XML, so it's different, but I don't think it has an impact on throw. My for-the-moment conclusion is the Yezl is the better thrower, probably attributable to the reflector, but by a small margin.
You cannot overlook the results here... A totally stock light doing 62.5 kcd on one cell at regulated amps of 2.5 is doing pretty good.
Beam Patterns
No pics yet, but compared side by side to the HD 2010, patterns are very similar - bright intense spot, surrounding flood zone. The spill zone is slightly smaller on the Yezl, to be expected because it appears to have the deeper reflector. Also the hot spot is ever so slightly smaller than the HD2010's, indoors that is.
There's a ringiness to the Yezl's beam, not in the HD2010's, both around the hot spot and at the outer edge of the spill. The HD2010 has the flower shape halo, but transitions are smooth. On the Yezl, the flower shape is not as defined - it's more round, but the ringiness is there.
Now about beams... This is with these 2 units I have here. There could or may be variations piece to piece about how the bezel and o-ring fit/mounted, how the reflector sits on the LED, etc. Also the Yezl appears to have an alignment piece that could block output, while the HD2010 has a pretty thin edged, low profile alignment piece - I won't know for sure until I dis-assemble it. Also, I could have caused the ringiness when I loosened the bezel to fix the bumped out o-ring. I had to use a strap wrench to loosen the bezel, but then I hand tightened it afterwards. To me, this level of ringiness is not so bad, definitely acceptable. I've seen much worse.
mudgripz - re-tested lumens with a Panasonic PF 18650 and get 901-867 lumens -- nearly identical as would be expected for an amp regulated driver.
Lens - definitely glass, size: 56.8mm x 2.04 mm
HD 2010 lens as comparison, size: 58 mm x 2.04 mm
Reflector - aluminum, size: 57 mm OD, 54 mm ID, 41mm depth
HD 2010 reflector as comparison, size: 57.75 mm OD, 51.5 mm ID, 38 mm depth
Hope this answered some questions. I'd say Joe was pretty dead-on with this light. His results of course may be different in what he saw, depending on the cells and amps being delivered in both the Yezl and HD2010 he used as a reference, specially the unregulated HD2010 that varies wildly depending on the cell used.